Configuring quota

Most of the quota backends have very similar configuration. They support two kinds of quota limits:

storage: Quota limit in kilobytes.

messages: Quota limit in number of messages. This isn't probably very useful.

You can configure quota globally by placing the settings in plugin section in dovecot.conf and you can give per-user limits by having your [:UserDatabase:userdb] return the quota setting as an [:UserDatabase/ExtraFields:extra field]. The userdb quota setting always overrides the global plugin setting.

The important thing to remember is to use the correct format for quota setting. You can't just return a numeric quota field from userdb and expect it to work. Dovecot wouldn't then know what quota backend to use.